Devices for in-vehicle navigational guidance to assist a driver traveling by vehicle from a current location of the vehicle to a desired destination have become an essential feature in modern vehicles. Such devices eliminate the burden of pre-planning or manual mapping of a driving route from a starting location to a desired destination. For example, U.S. Publ. 2010/0030471 (titled “Position detecting apparatus and method used in navigation system” to Watanabe et al. and published on Feb. 4, 2010, incorporated by reference herein) describes a position detecting apparatus, used in a navigation system for detecting a vehicle position, including an acceleration sensor, an angular velocity sensor and a dead reckoning calculating unit. Also see U.S. Publ. 2009/0115656 (titled “Systems and Methods for Global Differential Positioning” to Raman and Garin and published on May 7, 2009, incorporated by reference herein), which shows a device having micro-electromechanical system (MEMS) sensors, such as accelerometers and gyroscopes. The apparatus may be used as part of an in-vehicle navigational system to guide driving of a vehicle from a starting location to a desired destination. If not fixed to the vehicle, dead reckoning based on acceleration and angular velocity sensor measurements may become unreliable each time the apparatus moves in relation to the vehicle. Once moved, the dead reckoning calculations are based on sensor measurements from an unknown reference system.
The present disclosure provides aspects of improved apparatus and methods of accurate real-time navigational guidance for driving a vehicle from a current location to a desired destination and for detecting when sensor measurements become un-calibrated due to movement of the apparatus with respect to the vehicle.